Current Conditions at Sanborn Field
Monday: Clear sky. High: 72
Monday Night: Clear sky. Low: 48
Tuesday: Mostly sunny. High: 74
Tuesday Night: Becoming cloudy. Low: 54
Wednesday: Cloudy. Scattered showers possible. High: 72
Discussion:
Chilly mornings have arrived. Calm fall weather is expected in the early week; however, get ready for some rain later this week. A high pressure system will keep things calm at the beginning of the week. Winds will begin to pick up later Tuesday into Wednesday morning ahead of a low pressure system that will be making it's way into the area Wednesday. So make sure you bring that umbrella when you leave the house Wednesday. Expect rain chances to increase throughout the day with a possibility of evening storms.
-Baker
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Forecasters: Baker, Cade, Travis
Date Issued: 10/18/21 10:00 AM CST
Technical discussion:
Above average temperatures seem to be the theme for this fall, and we will continue to see this in the coming week. The main focus of this forecast is an amplified upper level ridge passing over Missouri Monday night, leading into another, smaller ridge on Tuesday. This will eventually give way to a Low Pressure system passing over the Upper Mississippi River Valley that brings with it the possibility for showers Wednesday into Wednesday night. Future forecasting shifts will want to watch this low to see how it may affect the area into Thursday. The model used for this forecast was GFS. Both GFS and NAM were running similarly, but GFS seemed to have a better hold on the ridge coming through.
At the 250 mb level, there is an amplified ridge from Minnesota to Kansas that will pass over Missouri on Monday night. On Tuesday, meridional flow continues with another ridge following the amplified one. This will lead to an upper level low moving over the Upper Mississippi River Valley Wednesday into Wednesday night. Winds stay southerly, and the jet stream dips down over Missouri over Wednesday-night into Thursday.
At the 500 mb level, Monday seems to be a boring day as there isn't much to see at this level. Similar to the 250 mb level, an amplified ridge is seen passing over. On Tuesday, a band of vorticity follows behind the ridge that passes over as the low moves into the Great Plains region. Wednesday is when the low moves over the Upper Mississippi River Valley and brings in a fair amount of vorticity and the chance for showers.
At the 700 mb level, very little moisture is seen on Monday, so dry conditions and clear skies are expected. Following behind the ridge, a small amount of moisture starts to build in on Tuesday. There doesn't appear to be enough to cause any precipitation, but it does give way to saturation on Wednesday, leading to the possibility of showers. 12z is when the most moisture develops, following just below the LPS.
At the 850 mb level, winds stay southerly from Monday to Tuesday, but begin to shift to the north on Wednesday. This, along with increased saturation at 700 mb, leads to suspicion of a cold front passing through, just underneath the LPS. Tuesday night, there also appears to be a slight LLJ flowing out of the south, which would be able to bring moisture to kick up some showers. The moisture transport vectors at this level back this up, showing moisture coming out of the Gulf at an increased magnitude Tuesday night into Wednesday.
At the sfc, again, winds are southerly over Monday and Tuesday and shift on Wednesday underneath the LPS, indicating frontal passage. The presence of solenoids over Monday and Tuesday indicates WAA, which is what helps keep temperatures above average. 6z GFS soundings also show above average temperatures, as well as chances for rain on Wednesday. Although the temperature and dew point lines aren't the closest, a K-index of 32 with PW of 1.14 inches indicate the chance for precipitation, leading to our forecast of scattered showers Wednesday into Wednesday night.
-Cade
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